Chop your onions and mince your garlic. Chop the celery, daikon radish, and potatoes.
Heat olive oil and butter in a large saucepan on medium-high heat. Add onions and garlic cloves and sauté gently until soft.
Add the turmeric powder and stir well. Add water or vegetable stock, celery, daikon radish, potatoes, salt, and black pepper, and bring to a boil. Reduce heat and simmer for 20-30 minutes, until the vegetables are well cooked.
Turn off the heat. Add the fresh parsley and stir it in. Use an immersion blender to puree four-fifths of the soup, leaving some vegetables whole for texture.
Combine arrowroot or cornstarch with cold water and stir into a slurry. Stir it into the hot soup as a thickener. Skip this step if you feel the soup is thick enough.
Taste, and adjust the amount of salt and pepper to your taste. Add a squeeze of fresh lemon or vinegar if you feel it needs the sour taste.
To Serve
If you feel it needs more punch, consider a squeeze of fresh lemon or a splash of white wine vinegar.Top with extra minced parsley for color and extra flavor.